Would you like to use automation in your electric distribution business, to maximize customer service, minimize outages and their duration, and to get the most bang for your buck from your delivery-system assets? Are you firmly committed down the path to an intelligent utility? If so, you will need a robust communications infrastructure.

Whether communicating within the substation to attain real operational automation, or sending information back to dispatch centers, line personnel and engineering departments, the key is the right information at the right time to the right person — or the right computer system. We must tap into all appropriate communication channels if we are to leverage the intelligent hardware and software that threatens to reform the way we view our industry.

The good news is there are many options to choose from, depending on your budget and other technical constraints. The bad news is there are many options to choose from, depending on your budget and other technical constraints.

THE PHYSICAL MEDIA

At first glance, communication choices can seem overwhelming, but the options all fit into one of two buckets: wired or wireless.

Wired options include: copper cable (twisted pair, CAT5), telephone line, coaxial cable, fiber-optic cable, power-line carrier (PLC) and broadband over power line (BPL). Wireless options include: paging, radio, cellular, wireless fidelity (Wi-Fi), satellite and microwave.

These technologies vary widely in cost and the technical issues can become complex. Twisted pair carrying sensor data is inexpensive, but in a substation environment with intense electromagnetic interference (EMI), the more costly fiber-optic cable is a better option, especially for long wire runs. Wired options have distance limitations, unless boosters (amplifiers) are added. Substations are outdoors, so ambient temperatures and weather are factors and can be intensely noisy during breaker and switch operations.

Mobile-phone service is relatively cheap, but is there coverage where the crews have to work? With satellite phones, coverage is rarely an issue, although the cost is high. Wi-Fi has limited range (for example, limited to the maintenance yard), but provides the capability of transferring messages and data between a truck and a company's Intranet and the Internet. Wireless options have limitations due to signal strength (a mobile phone works outside the building but not inside) and some require line of sight (there's a hill between the mobile phone and the only tower within range).

Bandwidth is an important limiting factor. How much data, including voice in digital form, must be communicated within what time frame? Don't plan on sending streaming video images over radio.

Reliability may be a critical factor. In the midst of a power outage, whether widespread or local to where the communications must take place, how important is it that the communications not fail? Is redundancy required? Does an alternate method need to be available? If so, how much time can elapse between the primary's failure and the alternate's availability?

It requires electricity to power the electronics that drive analog and digital signals across the communications' media. How will the electronics be powered, especially when there is a grid outage?

And, we can't forget the issue of security. The physical security for electronics and media, as well as cyber security from human interference with the communications' messages, are major considerations.

Hovering over the physical media are protocols: the rules for how the data are packaged and transmitted over the media and understood by the recipient. For example, there are many older “serial” protocols used with serial-based devices; DNP3 has become the most popular serial standard used for supervisory control and data acquisition (SCADA) systems.

The Internet protocol (IP)/Ethernet is the current, nonserial protocol of choice for a variety of reasons: standards, interoperability, performance and a wide availability of Ethernet-based devices. Such devices include intelligent electronic devices (IEDs), like relays, sensors and meters, and such diverse equipment as remote terminal units (RTUs), surveillance cameras and voice-over-IP (VoIP) phones. Local-area networks (LANs) and wide-area networks (WANs) are built with IP/Ethernet protocol.

COMMUNICATIONS WITH PEOPLE

When communicating with the line crew or troubleman, voice choices include telephone, paging, radio (in the truck), mobile phone and satellite phone. FirstEnergy (Akron, Ohio, U.S.), for example, recently switched from land mobile radio to Sprint's (Kansas City, Missouri, U.S.) Direct Connect. Text messaging using Wi-Fi, radio or cellular to a laptop in the truck or directly to a mobile phone is another option. Similar choices apply for field personnel initiating the conversation.

COMMUNICATIONS INVOLVING DATA

Data can originate from a person's actions, from sensors or from computer systems. Suppose a design engineer in the field creates a construction sketch on his laptop by revising a geographic information system (GIS) extract. How can he get that revision uploaded to GIS? Options include dial-in with a modem over telephone, plug-in to the company Intranet from a field office, cellular modem and Wi-Fi.

The amount of data is very large compared to a simple text message, so the main technical issue is bandwidth. Consider the step Exelon Energy Delivery (Chicago, Illinois, U.S.) took when it announced that it selected MapFrame (Dallas, Texas, U.S.) to fulfill the mobile mapping and field automation requirements of its mobile workforce management project in December 2006.

Actions can cause communications in the other direction as well. If an operator in the Energy Control Center wants to initiate a switching order, he requests the switch changes through a SCADA system. The order might be transmitted to a substation RTU via any of the wired options or to a pole-top RTU on a rural feeder via radio, cellular, PLC or satellite. In January 2007, JEA (Jacksonville, Florida, U.S.) decided to go with Open Systems International (Minneapolis, Minnesota, U.S.) to provide its next-generation energy management system (EMS).

Sensor data includes temperature, tap setting, voltage and current, and may be sent to an RTU for a batch transfer to a SCADA system or other computer systems. Sensor data can be transmitted by almost any wired or wireless media, but almost all technical issues must be considered in the choice of communication media. Last November, Santee Cooper (Moncks Corner, South Carolina, U.S.) chose Invensys Process Systems (London, England) to implement an InFusion-based SCADA system.

Data originating from a computer system frequently needs to be communicated to another computer system. For example, a smart meter can detect loss of power at the residence, one of the reasons CenterPoint Energy (Houston, Texas) licensed eMeter's (Redwood City, California, U.S.) Power Information Platform software to interface the utility's information systems in its intelligent grid limited deployment effort using BPL technology.

The loss of power is transmitted initially to the automatic meter reading (AMR) system, but other systems may need this fact: SCADA, EMS, distribution management system (DMS), outage management system (OMS), work management system (WMS) and dispatch system. Computer-to-computer communications are usually on fiber, coax or copper cable, since the computers are most likely interconnected as a LAN or WAN. At CPS Energy (San Antonio, Texas), ABB (Zurich, Switzerland) and MDSI (Richmond, British Columbia, Canada) are integrating ABB's Network Manager DMS and MDSI's Advantex products.

Due to its speed, microwave has been used for unit-tripping control actions, particularly in the Western United States, where sparse, long transmission lines and coal-fired base-load units abound. When one key transmission line is out of service, analytic studies show that the loss of a second key line will cause grid instability and a blackout. Tripping relays are armed so that if the second line fails, one or more generating units will be tripped within milliseconds to prevent the blackout — expensive technology, but justified.

COMMUNICATIONS WITHIN SUBSTATIONS

Substations serving low-density (rural) areas may not use any communications beyond sensor data transmitted via twisted pair to local meters. Larger substations serving high-density (urban) areas typically have an RTU inside the fence, gathering sensor data to transmit to a central site (SCADA, EMS, DMS) on a periodic basis (once per second).

Most installations today are using twisted pair or fiber to the RTU and dedicated telephone, radio or cellular to the central site. Some Wi-Fi and PLC have been installed for inside-the-fence communications. For example, Telkonet (Germantown, Maryland, U.S.) has installed its iWire System (PLC) at substations owned by four major U.S. public utilities.

Most installations today are still using DNP3 serial protocol, although Ethernet is gaining ground. A few new substations have been installed based on the new IEC 61850 standard, so that an Ethernet network over fiber exists within the substation, connecting all the intelligent devices together. In March 2005, Siemens (Erlangen, Germany) commissioned a Swiss substation control system based on IEC 61850.

This state-of-the-art installation is the basis for true substation automation, where control actions can be initiated by a computer system in the substation rather than a human in a central site. The key is bandwidth, obtained from high-speed fiber, because, for example, switching decisions require sensor data sampling rates faster than 1 msec.

Physical security concerns used to be relatively low priority, so that the only sensor might be a “gate-open” detection switch. Theft (copper wire, for example), vandalism and terrorism threats have made security a high enough priority to warrant substation video cameras, which require higher-bandwidth media to transmit images to a security desk.

There are companies that can assist with the problem of how to gradually migrate a substation with low-bandwidth media and serial protocols to higher bandwidth, security and Ethernet. Tampa Electric (Tampa, Florida) has installed substation-hardened switches from GarrettCom (Freemont, California) in substations where existing serial devices are incorporated into modern Ethernet-core substation networks.

SPECULATION ON THE FUTURE

While many will speculate on the future, a handful of industry experts have already offered their insight on the current and future usage and importance of communications to transmission and distribution operations.

Asked about current conditions, Tom Christopher, vice president of Electric Utility Business N.A. for Telvent (Madrid, Spain), said the classic SCADA market in the United States is very mature and that, therefore, the RTU is not dead. Most business today consists of retrofit installations, where companies have to accommodate several older serial protocols.

New installations typically use DNP3 serial protocol over wire and fiber. Andrew West, SCADA architect, Invensys Process Systems, who chairs the DNP technical committee, agrees, because utilities have such a large investment in installed equipment. Central systems (such as SCADA) do not last near as long as RTUs; therefore, replacement SCADAs must accommodate existing RTUs and their protocols.

Mark Dudzinski, marketing general manager for GE Energy's (Atlanta, Georgia, U.S.) transmission and distribution business, also believes that serial communications for IED and SCADA interfaces will be around for several years to come, because it is impractical and costly to upgrade communication infrastructures on a regular basis when new IEDs and protocols are available. GE is also providing a low-impact migration path in its transmission and distribution products and solutions from serial communications to the more prevalent IP architecture.

West sits on one of the IEC 61850 working groups and says we need to beware of marketing hype that states using IEC protocols is “really easy and cures everything.” He says there's a gap between what IEC 61850 can become and what it is today, and predicts that 61850 will become stable in two to three years. Today, 61850 is best for turnkey vendors, because it allows for standardized design of new substations — just scale them up or down, basically reuse the engineering. Christopher agrees that 61850 is promising and will likely be the “technology du jour” down the road, but U.S. utilities are currently focused on the economics: getting more life out of installed assets.

ABB spokesman Bob Fesmire believes the greatest importance of IEC 61850 simply may be that open standards usually encourage fairness: Small utilities with small financial leverage won't be limited to one vendor because of having to standardize on one proprietary protocol. IEC 61850 doesn't guarantee that any vendor's devices will plug-and-play with others, since 61850's requirements still need interpretation, but you can expect that different vendors' equipment can be more easily integrated together.

Dudzinski points out that GE Energy was one of the first suppliers to demonstrate an IEC 61850 implementation in 2006 and is offering IEC 61850 in its portfolio of protection, monitoring and control solutions. While much work has been done over the past 10 years to produce the IEC 61850 standard for IED communications, adoption of the standard by utilities and vendors is slow, and achieving all-encompassing interoperability between vendors is an issue.

All vendors recognize that communications are basic to advances in technology to support transmission and distribution operations. Christopher especially pointed out the baby-boom factor: utilities are facing the loss of knowledge capital (that is, people who know the physical systems inside out are about to retire).

Fiber in substations supports IEC 61850's requirements for data rates, but it is important to skeep an eye on advances in wireless and BPL. Dudzinski says that GE Energy is offering BPL technology for the substation, which enables utilities to transform existing substation low-voltage ac and dc electrical wiring into a low-cost, intelligent, high-speed broadband networking platform.

What about outside the substation? Today, the economics are not there because there is too much wire and there are too many devices. Dudzinski says that more work is required on defining communication standards and architectures outside the substation to support advanced distribution infrastructures and the vision of intelligent grids.